I have 6 children with mild to mid-severe adhd and i have done alot of research on it.
I have found a few reasons for it
1- food alergies, one child when he drinks milk or red 40 becomes so hyper he cannot controll himself
2- another was found to have high levels of mercury in his system due to vaccinations when he was a child
to say that it is a mental illness is incorect and i think we need to look at enviromental
some may be predesposed to the condition
autism has went up some 150% since we started using vaccines with mercury in them
just a little info
hope this helps someone